A ban is pretty harsh, how about taxing them heavily enough that they almost disappear? $1MM/billboard/year might be about right.
The reason people are asking for a ban of billboards is that they impose heavy externalities: they're distracting, ugly, et cetera. Capture those externalities rather than ban them.
what about a tax of incometimenumber * k ? (Oh wait, what does it mean to talk about a company or collective's income? What if you pay someone else to pay for the billboard? ok nevermind this is probably a terrible idea.)
The reason people are asking for a ban of billboards is that they impose heavy externalities: they're distracting, ugly, et cetera. Capture those externalities rather than ban them.